| English | Arabic | Home | Login |

Published Journal Articles

2020

Synthesis of Weinreb and their Derivatives (A-Review)

2020-04
Oriental Journal Of chemistry (Issue : 2) (Volume : 36)
Due to the large and efficient usage of Weinreb amides or N-methoxy-N-methyl amides as are remarkable intermediate in the organic synthesis field, the recent review paper provides a considerable development literature survey on the Weinreb amides synthesis. The direct transformation of carboxylic acids,acid chlorides, and esters to aldehydes or ketones employing organometallic reagents do not lead in high yields, since the high reactivity of ketone intermediates toward the organometallic reagents. While, the conversion to the appropriate Weinreb Amidesfollowed by treatment with the organometallic regent, result the stable expected ketones as the stable initial adduct toward further reactions. Furthermore, Weinreb amides undergo nucleophilic addition and produce a unique and steady five-membered cyclic intermediate which protects the over-addition, leading to a serious transformation.
2019

Recent Developments in Weinreb synthesis and their applications

2019-12
Oriental journal of chemistry (Issue : 6) (Volume : 35)
N-methoxy-N-methyl amides or Weinreb amides are worthy embranchment of amide group and their rich functional groups in organic synthesis become a strong else unfeasible conversion. Weinreb amides are produced as an intermediate product of the reaction of carboxylic acids, acid chloride or esters with organometallic reagents, which was first uncovered in 1981. The direct conversion of carboxylic acids or acid chlorides or esters to ketones or aldehydes using organometallic reagents do not lead in high yields, because the intermediate ketones are still highly reactive toward the organometallic reagent. However, after derivatization to the corresponding Weinreb Amide, reaction with organometallics does give the desired ketones, as the initial adduct is stabilized and doesn't undergo further reactions. Nucleophilic addition to the Weinreb amides results in a unique and stable five-membered cyclic tetrahedral intermediate which protects the over-addition, leading to a selective conversion.

Recent Advances in the Multi-component Synthesis of Pyrano[2,3-c]pyrazole derivatives

2019-09
Research Journal of Chemistry and Environment (Issue : 10) (Volume : 23)
This review highlights recent multicomponent reactions improvement in the synthesis of pyrano[2,3c]pyrazole derivatives in presence of different catalysts including sodium benzoate, CAN, AmberlystA21, L- or S-proline, CTACl, n-TiO 2 /H 14 [NaP 5 ], SiO 2 TMG,Fe 3 O 4 , DMAP, MS 4Å, DABCO, NH 4 H 2 PO 4 /Al 2 O 3 ,SnO 2 QDs, CAPB, BF 3 W 30 O 110 /MNPs, (Ni 0.5 Zn 0.5 Fe 2 O 4 @Hap-Cs 2 CO 3 ), VB 1 , ZrO 2 NPs,βCD,TUD, urea, NaBr, MMT-ZSA, piperidine, NMOAg 2 O, InCl 3 , PEG-400, NaF and SiO 2 . In this context, modern routes in the preparation and use of pyrano[2,3-c]pyrazole as a pioneer for the heterocyclic framework are based on three- or fourmulticomponent reaction of ethyl acetoacetate, hydrazine or phenylhydrazine, aromatic aldehyde and malononitrile substrates in the presence of a catalyst.

Evaluation of Crude oils and Natural Gases of Kurdistan-IRAQ by Catalytic Improvements to Lighter Oils using Local clays

2019-02
Ecology and the Envirenment (Volume : 222)
The chemical and physical properties of three different crude oils and two natural gas wells in Kurdistan-Iraq have been studied according to American Standard Test Method (ASTM) methods. Auto-distillations have been used to determine the changes in each cut, and gas–liquid chromatography has been used to find the approximate chemical constituents. A distribution diagram of paraffin, naphthenic, and aromatic hydrocarbons has been created. The gasoline cuts for each crude oil have been examined to find suitable octane additives (oxygenated or metal organic). The octane number increases as a function of the amount of additives, which has been plotted. A correlation between the trace metals and the types of hydrocarbons has been carried out for each crude oil. The improvement of these crude oils is achieved catalytically by reactions at high temperatures using different local clays, which gave us increases in lighter molecules by 7% (max). Chemical reactions are suggested for this improvement. X-ray analysis is also performed for each clay. Research is carried out on one gas–liquid well (Khor Mor) and another pure natural gas well. Gas chromatography analysis for Khor Mor shows 51% C1– C5 and 49% C6–C11, while other natural gas wells contain 98% methane. The natural gas of the Kirkuk wells contained approximately 10–12% hydrogen sulfide, which we separated using ethanolamines, and converted to hydrogen fuel and sulfur at two pilot plants using a new catalyst instead of the previous Clause process, producing about 143 tons of hydrogen per day.

Recent Free-Radical Reactions

2019-01
Asian J. Chem (Issue : 1) (Volume : 31)
This review highlights the most recent syntheses of free radical reactions, which included numerous processes (photoredox catalysis free-radical reactions, free-radical cascade processes reactions, Minisci-type free radical alkylation reactions and metal-catalysis free radical reactions). A photoredoxcatalyzed C–H functioning of aromatic heterocyclic utilizing an assortment of various, alkyltrifluoroborates has been mentioned. Utilizing organo-photocatalyst and a moderate oxidant, conditions malleable for functionalizing complex aromatic heterocyclics are outlined to prepare a oriental agent for late-stage derivatization. Radical alkylations of aromatic heterocyclic (Minisci reactions) appear a more direct functionalization of particular, C–H bonds. For the ground mentioned above, alkylation designing using radical have recently risen to significance for the late-stage functionalization of aromatic heterocyclic framework. Therefore, this issue is the primary point of the present survey, which thinks about work from the most recent five years. The work is ordered by the key procedures associated with the synthesis of free-radical reactions, planning to give researchers a simple comprehension of this free radical–reactions-based science and to give bits of knowledge to provide insights for further investigations.
2018

Shireen Mohammed, Recent Halocyclization Reactions of Alkenes - A Review,

2018-12
Indian Journal of Heterocyclic Chemistry, (Issue : 4) (Volume : 28)
This review highlights recent advances in catalytic enantioselective halofunctionalization of alkenes and explains the various planning to bring about regio- or stereoselective transformations. Halocyclization of olefinic substrates is an encouraging organization in creating O- and N-heterocyclic compounds, which additionally connotes the advancement of their asymmetric variations. The initiation of alkenes and their ensuing functionalization is an as often as possible utilized system in synthetic chemistry. The degree and difficulties of intra- and inter-molecular reaction variations have well talked about. The point is to give an outline of different reports, featuring the new reaction composes and techniques created amid the previous 5 years.

Evaluation of crude Oils and Natural Gases of Kurdistan-IRAQ by Catalytic Improvements to Lighter Oils using Local Clays

2018-12
WIT Transactions on Ecology and the Environment, (Volume : 222)
The chemical and physical properties of three different crude oils and two natural gas wells in Kurdistan-Iraq have been studied according to American Standard Test Method (ASTM) methods. Auto-distillations have been used to determine the changes in each cut, and gas–liquid chromatography has been used to find the approximate chemical constituents. A distribution diagram of paraffin, naphthenic, and aromatic hydrocarbons has been created. The gasoline cuts for each crude oil have been examined to find suitable octane additives (oxygenated or metal organic). The octane number increases as a function of the amount of additives, which has been plotted. A correlation between the trace metals and the types of hydrocarbons has been carried out for each crude oil. The improvement of these crude oils is achieved catalytically by reactions at high temperatures using different local clays, which gave us increases in lighter molecules by 7% (max). Chemical reactions are suggested for this improvement. X-ray analysis is also performed for each clay. Research is carried out on one gas–liquid well (Khor Mor) and another pure natural gas well. Gas chromatography analysis for Khor Mor shows 51% C1– C5 and 49% C6–C11, while other natural gas wells contain 98% methane. The natural gas of the Kirkuk wells contained approximately 10–12% hydrogen sulfide, which we separated using ethanolamines, and converted to hydrogen fuel and sulfur at two pilot plants using a new catalyst instead of the previous Clause process, producing about 143 tons of hydrogen per day.

Recent Trifluoromethylation Reactions. A Mini Review Paper

2018-06
Oriental Journal Of Chemistry, (Issue : 6) (Volume : 34)
This review highlights recent improvement in trifluoromethylene functionalization processes with CF3 reagents, includes: Togni’s, Umemoto’s, CF3SO2Cl, CF3I, Yagupol’skii-Umemoto, TMSCF3, Langlois (CF3SO2Na) and clarifies the several designing to result the corresponding trifluoromethylated products. In this article, the selective trifluoromethylation reactions with Togni’s reagents and their analogs are detailed, which work transition metals or photoactivated Ru or Ir catalysts as single electron giver to yield CF3 radical intermediate species. This issue is to introduce a draft of diverse reports, presenting the modern reaction collect and mechanics produced during the past five years. This task is demanded by the key protocol connected with the trifluoromethylation reactions, designing to sustain researchers a straight forward understanding of such reactions and to award information for further implements.

Schiff Bases Derived from 2-Hydroxynaphthalene-1-carbaldehyde and their Metal Complexes: A Review,

2018-06
Asian J. Chem (Issue : 6) (Volume : 30)
2-Hydroxynaphthalene-1-carbaldehyde is a key predecessor to an assortment coordinating agent and the Schiff bases derived from these ligands played a unique role in the development of important biomolecules which exhibit a widely range as a model system for biological macromolecules. Schiff bases formed from o-hydroxy aromatic ketones and aldehydes are stellar design for the study of keto-enol tautomerism in liquid and solid state. The metal-Schiff base complexes obtained from 2-hydroxynaphthalene-1-carbaldehyde had been revealed to show a broad area of biological effectiveness, catalytic reaction, sensors, selective electrodes and fluorescent.

Crown Ether Schiff bases and their Complexes: Recent Advances (A Review ),

2018-04
Oriental Journal Of Chemistry, (Issue : 4) (Volume : 34)
In latterly years, an interest in the synthesis of crown ether Schiff bases and their Complexes has been increased, due to the significance and broadly the uses of these compounds in various fields. In the present review paper outline extensive recent advances literature survey on the crown ether including azomethine gathering and their complexes with the tough and easy granter atoms, has been reconsidered. Assertiveness has been done on element complexation with crown ether holding Schiff bases to enable the researchers to procure valuable information of the chelating activity of crown ether containing azomethine gathering and their enforcement.
2017

A Flexible Protocol for the Preparation of Quinoline Derivatives through Mitsunobu Reaction and Aza-Wittig Intermediate,

2017-04
Indian Journal of Heterocyclic Chemistry, (Issue : 4) (Volume : 27)
A convenient procedure for the preparation of variously substituted quinolines is described. The new method is based on Mitsunobu reaction of aromatic amines with phosphonium yields. Facile onepot synthesis of quinolones derivatives involving an Aza-Wittig reaction of aryliminophosphorane with substituted aldehydes and cyclization of intermediates was achieved under basic conditions.

A Facile Synthesis of Quinazolinone derivatives throughVilsmeier intermediate,

2017-03
Indian journal of heterocyclic chemistry, (Issue : 1) (Volume : 27)
The reaction of ethyl 2-aminobenzoate with different substituted amide compounds led to cyclization through Vilsmeier intermediate in dry dichloromethane and ambient temperature, affording the 4(3H)-quinazolinone derivatives with higher yields. The structures of all the new products obtained in this work are supported by spectral and analytical data (infrared, nuclear magnetic resonance, and mass spectroscopy).

Synthesis and antimicrobial activities of some novel 2, 3-substituted -1,3-thiazolidin-4-ones derived from 2-amino-1,3-thiazole

2017-03
Asian journal of chemistry (Issue : 3) (Volume : 27)
New 2,3-substituted-1,3-thiazolidin-4-one (6a-f) were prepared by cyclocondensation of 2-[6-(4-chlorobenzyloxy)-2-naphthyliden]-4- (4-substituted phenyl)-5-methyl-1,3-thiazole (5a-f) and mercaptoacetic acid in benzene. The synthesized compounds were characterized on the basis of elemental analysis, 1H NMR, 13C NMR and FT-IR. The prepared compounds have been screened in vitro against two Grampositive Staphylococcus aureus, Staphylococcus epidermidis, and two Gram-negative Escherichia coli, Pseudomonas aernuginosa for antibacterial activity and two fungal strains Candida albicans, Candida krusei for antifungal activity using ciprofloxacin, ampicillin and ketoconazole with minimal inhibitory concentration (MIC) value of 10 mcg/L in DMSO. Compounds 6a and 6d showed good antibacterial and antifungal activities compared to reference medications utilized within this study.
2015

Metal Complexes of Schiff base from Salicylaldehyde Derivatives– A Review, International Journal of Current Research and Review. . 2015; 7(2): 06-16.

2015-12
IJCRR (Issue : 2) (Volume : 7)
Salicyaldehyde and their derivatives can be condensed with amines in 1:1 and 2:1 ratio to form bi, tri and tetra dentate NO and N2O2 Schiff base Ligands. They can contain additional donor atoms like oxygen, sulphur, nitrogen etc. which makes them Suitable chelating ligands to coordinate with Metal ions to form Schiff base complexes. Thus provides the possibility synthesis of large number of Schiff base complexes with divers’ structural feature. The model system including those with bidentate, tridentate and tetra dentate Schiff base derived from Salicyaldehyde and their coordination chemistry are summarized in this review.

Novel Free-Radical Mediated Carboalkenylation of Olefins Processes starting from ready available Benzylketone and Weinreb Amide Xanthate as a Electrophilic Radical Precursors and E-Sulfone Acceptor

2015-10
Indian journal of chemical society (Issue : 10) (Volume : 92)
The addition of electrophilic precursors such as benzylketone and weinreb amide xanthate across the double bond of unactivated olefins provides access to the corresponding three-component adducts in good to the excellent yields under mild conditions.

A Facile Protocol for the Construction of Tricyclic Framework Tetrahydrobenzo-4-nitrobenzenesulfonate, 4-methylbenzenesulfonate and [1,8] naphthyridine Substituents from Methyl δ-Lactam,

2015-04
Oriental journal of chemistry (Issue : 4) (Volume : 31)
A convenient procedure for the preparation of various naphthyridine constructions is described. The method is based on the Vilsmeier, cyclization and Suzuki reactions of piperidinone with substituted aniline. The reactions provided the desired fused tricyclic heterocycles products in high yields.

High Efficient of the Intermolecular Radical Reactions through three-Component Carbo-Oximation Process using new ready available Sulfonyl oxime

2015-03
Oriental journal of chemistry (Issue : 3) (Volume : 31)
Addition of functionalized carbon fragments across the olefinic π-system through a freeradical carbo-oximation process offers a straightforward access to valuable intermediatesfor organic synthesis. For this purpose, we designed a new protectedsulfonyl oxime, which enable rapid radical addition with high yields under mild conditions.

High Efficient of the Intermolecular Radical Reactions through three-Component Carbo-Oximation Process using new ready available Sulfonyl oxime

2015-03
Oriental journal of chemistry (Issue : 3) (Volume : 31)
Addition of functionalized carbon fragments across the olefinic π-system through a freeradical carbo-oximation process offers a straightforward access to valuable intermediatesfor organic synthesis. For this purpose, we designed a new protectedsulfonyl oxime, which enable rapid radical addition with high yields under mild conditions.

EVALUATION AND IMPROVEMENT OF DIESEL CUT FROM TAWKE CRUDE OIL WELLS, ZAKHO

2015-01
Science Journal Of University Of Zakho (Issue : 1) (Volume : 5)
The straight run diesel cuts of crude oil from T-8 and T-16 Tawke well-Zakho have been examined (qualitative and quantitative). Physical properties such as (density, API, viscosity, cloud point, flash point, water content, sulfur content…. etc.) of this crude oil and diesel product have been measured according to the ASTM method. To improve chemical constituents of these crude oils and increasing the diesel distillation volume cuts by using three types of local clays, X-Ray fluorescence spectroscopy analysis of these clays have been done, a series experiments have been done at a different percentage of local clays and different time of reflux for Tawke wells T-8 and T-16 crude oil. These experiments were performed, in order to optimize the best clay and percentage, as well as finding the suitable reflux time to enhance the volume of the fraction at (200-320) °C. The figures have been plotted to find the optimum percentage weight for each clay, time of reflux, and temperatures. The change in chemical constitutes of these crude oils have been monitored by gas chromatography and tabulated in tables.
2014

Synthesis, Charactrization and Biological Activity of Some Schiffbases Derived from 2-amino-6-subistituted -1,3-Benzothiazole and 6-alkoxy -2Naphthaldehyde,

2014-12
Journal of green and herbal chemistry, (Issue : 1) (Volume : 4)
A series of 2-amino-6-substituted-1,3-benzothiazole derivatives were synthesized and Schiff bases were prepared by reacting of 6-alkoxy-2-naphthaldehyde 3a-b with 2-amino-6-substituted-1,3-benzothiazole 2a-e to form a number of potentially biologically active compounds 4a-i.The structures of 2-amino-6-substituted-1,3- benzothiazole and Schiff bases were confirmed by using FT-IR, 1 H-NMR 13CNMR and C,H,N- elemental analysis. The purity of the individual compounds was confirmed by TLC. The prepared compounds were tested against representatives of gram-positive, gram – negative bacteria and antifungal by the agar diffusion method.
2013

chelating ion exchange properties of polyurethane resin derived from thiazolo(5,4-D) thiozole,

2013-12
journal of natural science research (Issue : 11) (Volume : 3)
3,6-dihydrothiazolo [5, 4-d] thiazole which supported on polyurethane was synthesized. The prepared compound was characterized by FTIR and 1H NMR spectroscopy. The chelating properties towards various metal ions Pb2+, Mn2+, Cr3+, Co3+and Cd+3 was examined. The effects of the concentration of metal ions, time of extraction and pH as well as the recovery of ions have been studied. The results showed that the high activity order of resin to extract the metal ions is Pb2> Cd+3 > Mn2+>Cr3+> Co3+.

Syntheses and BiologicaActivity of Copper(II), nickel(II), and Cobalt(II) with tetradenate Schiff BaseComplexes derived from 2-hydroxy-1-naphthaldehyde and aromatic Diamines,

2013-12
UOZJ, (Issue : 1) (Volume : 1)
2-hydroxy-1-napthaldehyde reacted with diaminophenol in absolute EtOH in a ratio 2:1 to give new Schiff bases (H2L1, H2L2 and H2L3). The obtained Schiff bases which were in tautomeric equilibrium (enol-imine O-H…N, keto-amine O…H-N forms) were used as ligands to coordinate Cu (II), Ni (II), and Co (II) leading complexes. The ligands and the complexes were characterized by physicochemical, elemental and spectroscopic analyses. The complexes exhibited 1:1 metal to ligand coordination ratio ( ML1) , (ML2), (ML3). Both Ligands and complexes were evaluated for antibacterial properties using disc diffusion method.. The complexes showed higher activity than the free ligands.

Effect of surface treatment on the Biaxial Flexural Strengthof High Leucite Feldspathic Porcelains,

2013-12
Tikrit Journal of Dentistry (Issue : 1) (Volume : 3)
The purpose of this study was to examine the effect of altering surface topography on the biaxial flexural strength (BFS) of four dental ceramics, Mirage (MI), Flexoceram (FL), Optec-HSP (OP) and IPS Empress (EM).Twelve groups of ten discs 123mm were prepared and fired according to the manufacturers' instructions. Ten specimens of each material were subjected to three surface treatments, polished, grit blasted and etched with 10% hydrofluoric acid (HF) for 2 minutes. Some specimens were gold coated for examination under Scanning Electron Microscope (SEM). BFS was determined using Lloyd M5K universal testing machine at a cross-head speed of 0.5 mm/min. A one-way ANOVA was used to evaluate the differences between groups.The results obtained showed that the only significant difference in the BFS was the 10% HF for OP and FL (One-way Anova, P<0.05). The decrease in BFS is most likely due to an increased surface flaw size, such that surface initiated crack growth dominates over the bulk internal flaw size of the ceramics.The BFS of dental porcelain used in this study may be governed either by the internal or surface flaws depending on the manner of surface preparation. Specimens etched with 10% HF became weaker for OP and FL ceramics.
2012

improvement of petroleum of Tawke crud oil wells using local clays, Zakho

2012-12
JPGER (Issue : 4) (Volume : 2)
Evaluation of Tawke crude oil TW4 and TW8 through distillation cuts have been done by analysis chemical constituent (Gas chromatography) and measuring the (density, API, viscosity, pour point, flash point, water content, sulfur content, ash content etc., according to both ASTM and IP methods). Improvement of this crude oil TW4 and TW8 have been done using three types of local clay. X-Ray analysis of these clays have been done and the chemical analysis of crude oil performed and compared before and after refluxing this crude oil using gas – chromatography. A series of experiments have been done at a different percentage of clay, at the different time of reflux and different temperatures and the changes in the chemical constituent of this crude oil monitored by gas – chromatography analysis. Also, Octane number of the distilled between (34 -200) °C have been measured.

The effect of CNT doping on the hydrogenation behavior of Y 5 Si3

2012-12
Iraqi National Journal in Chemistry, (Issue : 12) (Volume : 45)
The reactivity of the CNT-doped Y5Si3 compared to Y5Si3 phase system has been investigated. Both alloys have been prepared by arc melting and their reactivity with hydrogen has been studied. Single–phase CNT-doped Y5Si¬3 can only be made by melting preformed Y5Si¬3 with the CNT. An activation process has been developed to induce reaction of the doped alloy with hydrogen. It involves cycling in H2 gas pressures above 1.2 atm at the temperature higher than 435oC depending on the CNT content. Conditioned samples, will repeatedly (above 50 cycles) cycles 2.5 H (fu)-1 between room temperature and 500oC with 0.9 and 1.2 H (fu)-1 being desorbed and absorbed with fast kinetic within a very small temperature range. This behavior is believed to arise from the polymorphic change between an α-form of the D88 structure and a supercell β-form. An attempt to quantify the enhanced stability, compared to Y5Si3, is made by measuring reaction enthalpies using Can't Hoff isopleths.

Fabrication and characterization of calcium phosphate/Zirconia composite,Intrnational Researchjournal of Biothechnology,

2012-12
Intrnational Research journal of Biothechnology, (Issue : 7) (Volume : 3)
The aim of this study is to fabricate high strength calcium phosphate/ yttrium partially stabilized zirconia (Y-PSZ) composites using a simple powder pressing technique. Various compositions of hydroxyapatitesymbol 210 \f "Symbol" and zirconia power symbol 211 \f "Symbol", ranging from 10 to 90 wt% Y-PSZ, were prepared using a wet mixing process. Ten compacts (13.5mmsymbol 180 \f "Symbol"3mm) were made for each composition, pressed and fired in air at sintering temperatures from 1100 to 1450oC for up to 12 hours. The bulk density, true porosity, linear shrinkage and biaxial flexural strength (BFS) were measured using standard methods. Microstructural changes were examined using XRD, DTA, and SEM. The true porosity reduced and linear shrinkage increased with increasing sintering temperature and amounts of zirconia, whereas the firing time had little effect. The highest mean value achieved for the BFS was 269symbol 177 \f "Symbol"20 Mpa for a composition of 70% Y-PSZ, fired at 1450oC for 6 hours, however with the hydroxyapatite (Hap) decomposed to symbol 97 \f "Symbol"-TCP. XRD and DTA data show an interaction between the zirconia and the Hap at the temperature lower than changes normally encountered for pure Hap. We conclude that sintering temperature and composition affect the densification behavior of calcium phosphate/Y-PSZ composites. The BFS increases with a reduction of porosity and increases with both sintering temperature and additions of zirconia. It was noted that there is considerable scope for improvement in the BFS values by reducing the porosity of these composites. Further work is needed to elucidate the microstructural changes.

evaluation and improvement of gasoline and naphtha cut of Tawke crude oil wells, Zakho,

2012-12
JPGER (Issue : 4) (Volume : 2)
Gasoline cuts have been separated from crude oil of Tawke wells (fourth and eighth) according to ASTM method at one atmosphere. Physical properties of each gasoline have been determined. Also, chemical constituents of this gasoline have been examined using gas chromatography and compared with Naphtha Tawke Refinery. Percent of each straight run gasoline from crude oil of both wells have been determined with their Octane Numbers (RON and MON). The current research has been performed to increase the Octane Number of both gasoline and Naphtha using series of oxygenated and organometallic additives. Also, mixed additives of oxygenated and organometallic have been added to this gasoline and Naphtha in order to find the enhancement in Octane Number. These mixtures give more increases in Octane Number than pure oxygenated or organometallic additives.
2011

effect of Heat treatment and Phase change onBFS of two hydroxyapatite ceramic powders

2011-12
Iraqi national Journaofchemistry, (Issue : 10) (Volume : 44)
Thermal stability and sintering behavior of two hydroxyapatite (HAP) powder were designated. AHAP and BHAP have been investigated at the fired sintering temperature range from 1100 to 1450 of for 3 hrs using XRD and IR spectroscopy. The fired compacts have been characterized by measuring their bulk density, firing shrinkage and biaxial flexural strength (BFS). BHAP has been found to transform to oxyhydroxyapatite (OHAP) at T≥1200oC, and at T≥1300oC started to decompose to β-tricalcium phosphate (β-TCP). AHAP has been found to be marginally less stable than BHAP with OHAP forming at T≥1150oC and βTCP forming at T≥1200oC. In both materials, β-TCP transformed to α-TCP at T ≥1350oC. Maximum densification (∼95% of theoretical density) occurred at a lower firing temperature for AHAP (1150oC) than for BHAP (1250oC), with AHAP also showing a slightly higher firing shrinkage (23% compared with 20% for BHAP). The BFS of both materials has been found to increase with increasing sintering temperature up to 1300oC, reaching a maximum value of ∼90-100 MPa. At T≥1300oC, this is followed by the rapid reduction in BFS due to cracks forming as a result of a volume increase associated with the transformation of β-TCP into α-TCP. It has been concluded that BHAP is marginally more thermally stable than AHAP, while the latter densifies at a lower firing temperature, this is not a disadvantage and comparable properties can be achieved for both powders, although different firing conditions need to be used.
1990

1 H and 13 CNMR study ofNew Class of Bipyridium liquid Crystals,

1990-12
Spectroscopy letters (Issue : 7) (Volume : 23)
1H and 13C NMR, as well as UV and IR, spectra of a new class of bipyridinium salts made by double quaternization of trans−1, 2-bis(4-pyridyl) ethene unit with n-alkyl salts are reported. The effect of quaternization on the 1 and 13C NMR spectra of the salts is discussed

Back